Alkylation (combining isoparaffins with light olefins to make high-octane alkylate) typically employs which catalyst system in refinery practice?

Introduction:
Alkylation reacts isobutane with olefins (e.g., propylene, butylenes) to produce a premium gasoline blendstock called alkylate, prized for high octane and low vapor pressure. Choosing the correct catalyst is central to unit design and safety protocols.

Given Data / Assumptions:

• Feed: isobutane plus C3–C4 olefins.
• Desired product: branched C7–C9 isoparaffins (alkylate).
• Question: which catalyst system is typically employed.

Concept / Approach:
Commercial alkylation has historically used strong liquid acids as catalysts—either sulphuric acid (H2SO4) or hydrofluoric acid (HF). Many refineries operate H2SO4 units due to handling considerations, though HF is also used. Among the listed options, sulphuric acid is the correct, widely implemented catalyst.

Step-by-Step Solution:
1) Identify hallmark alkylation catalysts: H2SO4 or HF.2) Check options: only sulphuric acid matches the commercial choices.3) Select sulphuric acid.

Verification / Alternative check:
Industry practice, licensor documentation, and safety literature consistently reference sulphuric acid and HF as the two mainstream technologies for isobutane alkylation.

Why Other Options Are Wrong:
Nickel, silica gel, alumina, zinc oxide: These are used for other purposes (hydrotreating, adsorption, supports), not as the strong acid catalyst for liquid-phase alkylation.

Common Pitfalls:
Confusing isomerisation catalysts or FCC catalysts with alkylation acids; alkylation requires a very strong acid medium to generate carbocations and drive the reaction pathway.

Final Answer:
Sulphuric acid